Position Detection System, Position Detection Method, Angle Detection Method, and Marker

ABSTRACT

To provide a position detection system, a position detection method, an angle detection method, and a marker that enable detection of a position, adjustment of a position, detection of an angle, and the like of a movable body with respect to a stationary body to be easily performed. Means for solving problem: A position detection system is a position detection system for detecting a position N of a movable body moving with respect to a stationary body, the position detection system including a light source provided in one of the stationary body and the movable body, an imaging unit provided in one of the stationary body and the movable body, a marker provided in the other of the stationary body and the movable body, and a position detecting unit configured to detect a position of the movable body with respect to the stationary body based on luminance of an image of the marker acquired by the imaging unit, wherein the marker includes a reflective layer, and a light control layer provided in the reflective layer, and the light control layer transmits light having an angle of incidence with respect to the main surface being within a predetermined threshold value.

TECHNICAL FIELD

One aspect of the present disclosure relates to a position detectionsystem, a position detection method, an angle detection method, and amarker.

BACKGROUND ART

A demand has been made for detecting a position of a movable body movingwith respect to a stationary body. For example, Patent Document 1describes a flight body as a movable body that accurately detects apositional relationship between the flight body and a landing locationunit as a stationary body to land on the landing location unit. Amillimeter wave radar device provided in the landing location unitcaptures and tracks the flight body to detect a positional relationshipbetween the flight body and the landing location unit according toPatent Document 1.

CITATION LIST Patent Documents

Patent Document 1: JP 11-72558 A

SUMMARY Technical Problem

However, detection of a positional relationship between the flight bodyand the landing location unit by emitting a radio wave such as amillimeter wave radar cannot be performed at the time of a breakdowncaused by a disaster or when an energy supply is lost. As such, therehas been a demand for easily performing detection of a position,adjustment of a position, detection of an angle and the like of a movingbody with respect to a stationary body.

Solution to Problem

A position detection system according to an aspect of the presentdisclosure is a position detection system for detecting a position of amovable body moving with respect to a stationary body, the positiondetection system including a light source provided in one of thestationary body and the movable body, an imaging unit provided in one ofthe stationary body and the movable body, a marker provided in the otherof the stationary body and the movable body, and a position detectingunit configured to detect a position of the movable body with respect tothe stationary body based on luminance of an image of the markeracquired by the imaging unit, wherein the marker includes a reflectivelayer, and a light control layer provided in the reflective layer andincluding a main surface, and the light control layer transmits lighthaving an angle of incidence with respect to the main surface beingwithin a predetermined threshold value.

A position detection method according to an aspect of the presentdisclosure is a position detection method for adjusting a position of amovable body moving with respect to a stationary body, the methodincluding the steps of emitting light from a light source provided inone of the stationary body and the movable body to a marker provided inthe other of the stationary body and the movable body, acquiring animage including the marker, and detecting a position of the movable bodywith respect to the stationary body based on luminance of an image ofthe marker acquired, wherein the marker includes a reflective layer, anda light control layer provided in the reflective layer and having a mainsurface, and the light control layer transmits light having an angle ofincidence with respect to the main surface being within a predeterminedthreshold value.

An angle detection method according to an aspect of the presentdisclosure is an angle detection method for detecting a relative anglewith respect to a target, the method including the steps of emittinglight from a light source to a marker provided in the target, acquiringan image including the marker, and detecting the relative angle withrespect to the target based on luminance of an image of the markeracquired, wherein the marker includes a reflective layer, and a lightcontrol layer provided in the reflective layer and including a mainsurface, and the light control layer transmits light having apredetermined angle of incidence with respect to the main surface.

A marker according to an aspect of the present disclosure is a markerincluding a reflective layer, and a light control layer provided in thereflective layer and including a main surface, wherein the light controllayer transmits light having an angle of incidence with respect to themain surface being within a predetermined threshold value, the lightcontrol layer includes at least two regions, and the threshold values ofthe two regions are different from each other, and the reflective layerreflects light having passed through the light control layer, andluminance of the reflected light is used to detect a position of themarker.

Advantageous Effects

According to an aspect of the present disclosure, detection of aposition, adjustment of a position, detection of an angle, and the likeof a movable body with respect to a stationary body can be performedeasily.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration view illustrating a positiondetection system according to an embodiment of the present disclosure.

FIG. 2 is a block diagram illustrating a block configuration of theposition detection system.

FIG. 3A is a perspective view of a marker, and FIG. 3B is a graphillustrating a relationship between a viewing angle of an imaging unitand luminance (luminance) of the marker in an image.

FIGS. 4A to 4D are views for explaining a relationship between an angleof incidence and reflection of light in each region.

FIG. 5A is a view illustrating an end face of a light control layer 4,and FIG. 5B is a view of the light control layer 4 from a thicknessdirection.

FIG. 6 is a view illustrating a light control layer according to amodified example.

FIGS. 7A to 7D are views for explaining retroreflection.

FIGS. 8A to 8C are views illustrating a laminate structure of a marker.

FIGS. 9A to 9C are views illustrating a modified example of a marker.

FIG. 10 is a flowchart illustrating processing details of a computationunit.

FIG. 11 is a flowchart illustrating processing details of a computationunit.

FIG. 12 is a flowchart illustrating processing details of a computationunit.

FIG. 13 is a flowchart illustrating processing details of a computationunit.

FIGS. 14A to 14D are views illustrating a marker in an image.

FIGS. 15A to 15F are views illustrating a marker according to a modifiedexample.

FIG. 16 is a view illustrating a light control layer according to amodified example.

FIGS. 17A to 17C are views illustrating a light control layer accordingto a modified example.

FIGS. 18A to 18D are views for explaining measurement of a vibrationfrequency and inclination.

FIGS. 19A and 19B are views for explaining measurement of a vibrationfrequency and inclination.

FIG. 20 is a flowchart illustrating a procedure for measurement of avibration frequency and inclination.

FIGS. 21A and 21B are views for explaining measurement of a vibrationfrequency and inclination.

FIGS. 22A and 22B are views illustrating other examples of use of amarker.

DESCRIPTION OF EMBODIMENTS

Detailed descriptions of the embodiments according to the presentdisclosure are given below with reference to the attached drawings. Notethat in the description of the drawings, identical or equivalentelements are denoted by the same reference signs, and duplicatedescriptions of such elements are omitted.

FIG. 1 is a schematic configuration view illustrating a positiondetection system 100 according to an embodiment of the presentdisclosure. As illustrated in FIG. 1, the position detection system 100includes a flight body 1 (movable body), a base station 2, and a marker3 provided in a landing location unit AP (stationary body). The positiondetection system 100 is a system configured to detect a position of theflight body 1 that moves with respect to the landing location unit APhaving a position fixed, and to guide the flight body 1 to adjust theposition of the flight body 1. A position of the moving body withrespect to the stationary body to be detected may be any form ofinformation as long as a relative positional relationship between theflight body 1 and the stationary body can be comprehended.

The flight body 1 is an unmanned aerial vehicle such as a drone. Theflight body 1 is capable of self-sustained flight. The flight body 1includes a main body unit 10, a propeller unit 11, a camera 12 with alight source, and a transmission/reception unit 13 configured to performcommunication. The main body unit 10 includes a frame constituting theflight body 1, an exterior, an internal mechanism, an electronic device,and the like. The propeller unit 11 rotates to generate lift force andthrust force.

The camera 12 with a light source is an electronic device into which alight source 17 configured to irradiate with light and an imaging unit18 configured to acquire an image are integrated. The light source 17irradiates with light downward from the main body unit 10. The imagingunit 18 acquires an image of a location irradiated with light by thelight source 17. In the present embodiment, the light source 17irradiates the marker 3 with light during landing. Furthermore, theimaging unit 18 acquires an image of the marker 3 irradiated with light.The light source 17 emits light in a direction perpendicular to ahorizontal plane of the flight body 1. As illustrated in FIG. 4A, ahorizontal plane FP of the flight body 1 is a reference plane of theflight body 1, and is a virtual surface that spreads in the horizontaldirection when the flight body 1 lands on a horizontal ground surface.An optical axis L1 of light emitted by the light source 17 isperpendicular to the horizontal plane FP. Furthermore, an optical axisL2 of the imaging unit 18 is also perpendicular to the horizontal planeFP.

The transmission/reception unit 13 transmits and receives informationwirelessly to and from the base station 2. A plurality of the basestations 2 are scattered over each place in an area in which the flightbody 1 can fly. Accordingly, the transmission/reception unit 13communicates with the base station 2 nearest the flight body 1.

FIG. 2 is a block diagram illustrating a block configuration of theposition detection system 100. As illustrated in FIG. 2, the flight body1 includes the above-described light source 17, the above-describedimaging unit 18, the above-described transmission/reception unit 13, astorage unit 19, and a computation unit 20. The storage unit 19 includesa built-in memory, an external memory, and the like, and stores varioustypes of information.

The computation unit 20 is a unit configured to perform various types ofcalculation of the flight body 1. The computation unit 20 includes aprocessor, a memory, and the like. The processor is a computing unitsuch as a Central Processing Unit (CPU). The memory is a storage mediumsuch as a Read Only Memory (ROM) and a Random Access Memory (RAM). Thecomputation unit 20 implements various functions by loading a programstored in a ROM onto a RAM, and executing with the CPU the programloaded onto the RAM. The computation unit 20 includes an imageacquisition unit 21, a position detecting unit 22, and a positionadjustment unit 23.

The image acquisition unit 21 acquires an image by reading an imagecaptured by the imaging unit 18. When the flight body 1 lands, the imageacquisition unit 21 acquires an image of the marker 3. The positiondetecting unit 22 detects a position of the flight body 1 with respectto the landing location unit AP based on luminance of the image of themarker 3 captured by the imaging unit 18 and acquired by the imageacquisition unit 21. The position adjustment unit 23 adjusts theposition of the flight body 1 based on the result of the detectionperformed by the position detecting unit 22. The position adjustmentunit 23 guides the flight body 1 such that the flight body 1 can land ina horizontal attitude at a position of the landing location unit AP.Then in a stage in which the position and the attitude are in order, theposition adjustment unit 23 causes the flight body 1 to land in thelanding location unit AP. Note that details of processing of theposition detecting unit 22 and the position adjustment unit 23 will bedescribed after the marker 3 is described.

The base station 2 includes a computation unit 31, a storage unit 32,and an input/output interface 33. The computation unit 31 is a unitconfigured to perform various types of calculation in the base station2. The storage unit 32 stores various types of information. Theinput/output interface 33 includes an information input device such as akeyboard, a mouse, and a touch panel, and an information output devicesuch as a display and a speaker. The storage unit 32 of the base station2 may store information of the marker 3 provided in the landing locationunit AP scattered over each place. For example, the base station 2 maytransmit to the flight body 1 position information of the landinglocation unit AP which is to be the destination and information of themarker 3 provided in the landing location unit AP. Furthermore, thecomputation unit 31 of the base station 2 may perform some of theprocessing to be performed by the computation unit 20 of the flight body1, and transmit the calculation result to the flight body 1.

Next, a detailed configuration of the marker 3 according to the presentembodiment will be described with reference to FIGS. 3A and 3B and FIGS.4A to 4D. FIG. 3A illustrates a perspective view of the marker 3. FIG.3B is a graph illustrating a relationship between a viewing angle of theimaging unit 18 and luminance (luminance) of the marker 3 in an image.FIGS. 4A to 4D are views for explaining a relationship between an angleof incidence and reflection of light in each region.

As illustrated in FIGS. 4A to 4D, the marker 3 includes a reflectivelayer 5 configured to reflect light and a light control layer 4 providedin the reflective layer 5. The reflective layer 5 is a layer configuredto perform retroreflection in which incident light is reflected along anoptical path of the incident light. The details of the retroreflectionwill be described below.

The light control layer 4 is a layer configured to transmit light havingan angle of incidence with respect to a main surface 4 a being within apredetermined threshold value. “To transmit light having an angle ofincidence being within a predetermined threshold value” refers totransmitting light having an angle of incidence being within apredetermined range at transmissibility equal to or more than apredetermined transmissibility, and transmitting light having an angleof incidence outside the predetermined range at transmissibility equalto or less than the predetermined transmissibility. Furthermore, thelight control layer 4 transmits light to emit reflected lightretroreflected by the reflective layer 5 from the main surface 4 a. As aresult, the imaging unit 18 acquires, as an image of the light controllayer 4, an image indicated by luminance of the reflected light. Thelight control layer 4 includes at least two regions E1, E2. Thresholdvalues of the two regions E1, E2 are different from each other.Specifically, as illustrated in FIG. 3A, when an X-axis and a Y-axis areset in the horizontal direction and a Z axis is set in the verticaldirection, the marker 3 includes four sections having two rows and twocolumns within an X-Y plane. Of these, a section on the negative side inthe X-axis direction and the positive side in the Y-axis direction isset as a region E1 (may also be referred to as a second quadrant QD2) ofthe light control layer 4, and a section on the positive side in theX-axis direction and the negative side in the Y-axis direction is set asa region E1 (may also be referred to as a fourth quadrant QD4) of thelight control layer 4. A section on the negative side in the X-axisdirection and the negative side in the Y-axis direction is set as aregion E2 (may also be referred to as a third quadrant QD3) of the lightcontrol layer 4, and a section on the positive side in the X-axisdirection and the positive side in the Y-axis direction is set as aregion E2 (may also be referred to as a first quadrant QD1) of the lightcontrol layer 4.

As illustrated in FIG. 4B, the region E1 of the light control layer 4transmits light having an angle of incidence in the Y-axis direction (anangle of incidence as viewed from the X-axis direction) being within athreshold value θ, based on light perpendicularly incident on the mainsurface 4 a. Furthermore, luminance of light passing through the regionE1, as light perpendicular to the main surface 4 a being the peak,gradually decreases as the angle of incidence increases. The lightcontrol layer 4 blocks light having an angle of incidence in the Y-axisdirection being larger than the threshold value θ without transmittingthe light. On the other hand, as illustrated in FIG. 4C, the region E1of the light control layer 4 transmits light without particularrestriction with regard to an angle of incidence in the X-axis direction(an angle of incidence as viewed from the Y-axis direction) as long asthe angle of incidence in the Y-axis direction is equal to or less thanthe threshold value θ. As illustrated in FIG. 4D, the region E2 of thelight control layer 4 transmits light having an angle of incidence inthe X-axis direction (an angle of incidence as viewed from the Y-axisdirection) being within the threshold value θ, based on lightperpendicularly incident on the main surface 4 a. Furthermore, luminanceof light passing through the region E2, as light perpendicular to themain surface 4 a being the peak, gradually decreases as the angle ofincidence increases. The light control layer 4 blocks light having anangle of incidence in the X-axis direction being larger than thethreshold value θ without transmitting the light. On the other hand, asillustrated in FIG. 4A, the region E2 of the light control layer 4transmit light without particular restriction with regard to an angle ofincidence in the Y-axis direction (an angle of incidence as viewed fromthe X-axis direction) as long as the angle of incidence in the X-axisdirection is equal to or less than the threshold value θ. Note that inany of the regions E1, E2, an angle equal to or less than the thresholdvalue θ includes a reference angle of 0°, namely, an angle perpendicularto the main surface 4 a.

Due to the relationship described above, as illustrated in a graph G1 ofFIG. 3B, luminance of the region E1 in an image captured by the imagingunit 18 peaks at a viewing angle (equal to an angle of incidence oflight from the light source 17) of 0° perpendicular to the main surface4 a, and decreases gradually as a viewing angle in the Y-axis directionincreases, and becomes substantially 0 when the viewing angle exceedsthe threshold value θ. On the other hand, as illustrated in a graph G2of FIG. 3B, the luminance of the region E1 in the image is constantregardless of the viewing angle in the X-axis direction. Note that theluminance of the graph G2 is substantially constant at luminance that isaligned with the peak of the graph G1 but corresponds to the viewingangle in the Y-axis direction. Furthermore, as illustrated in the graphG1 of FIG. 3B, luminance of the region E2 in an image captured by theimaging unit 18 peaks at a viewing angle of 0° perpendicular to the mainsurface 4 a, and decreases gradually as a viewing angle in the X-axisdirection increases, and becomes substantially 0 when the viewing angleexceeds the threshold value θ. On the other hand, as illustrated in thegraph G2 of FIG. 3B, the luminance of the region E2 in the image isconstant regardless of the viewing angle in the Y-axis direction.

Next, a configuration of the light control layer 4 will be described indetail with reference to FIGS. 5A and 5B and FIG. 6. FIG. 5A is a viewillustrating an end face of the light control layer 4, and FIG. 5B is aview of the light control layer 4 viewed from a thickness direction. Thelight control layer 4 is a member that is a so-called louver film. Thelight control layer 4 is a layer including a non-transmissive portion 4Bincorporated into a transmissive portion 4A. The transmissive portionincludes a polymer resin or the like having high transparency, and thenon-transmissive portion 4B is minute and referred to as a louver. Thenon-transmissive portion 4B is provided within the transmissive portion4A at a constant pitch in one direction in a planar direction (thevertical direction in FIGS. 5A and 5B, and hereinafter may be referredto as an “arrangement direction”). In the form illustrated in FIGS. 5Aand 5B, the non-transmissive portion 4B is formed in an entire region inthe thickness direction of the transmissive portion 4A. Furthermore, aplurality of the non-transmissive portions 4B extend parallel to eachother along a direction orthogonal to the arrangement direction.

Such a light control layer 4 blocks light in an oblique direction out ofthe incident light by the non-transmissive portion 4B. Namely, lightincident perpendicularly or at a small inclination angle on the mainsurface 4 a of the light control layer 4 (light traveling in a directionindicated by D1 in the figure) passes through the transmissive portion4A. Note that the light having passed through the transmissive portion4A is reflected by the reflective layer 5 at a position of a mainsurface 4 b. On the other hand, light incident in the oblique directionon the main surface 4 a at an angle greater than a threshold value(light traveling in a direction indicated by D2 in the figure) isblocked by the non-transmissive portion 4B. Note that light to beincident from a position of the non-transmissive portion 4B out of themain surfaces 4 a is blocked at the position of the main surface 4 a. Asa result, the light control layer 4 has a function of controlling adirection of travel of light passing through the transmissive portion 4Ain a predetermined angular range, and to provide uniform luminancedistribution.

In this light control layer 4, the transmissive portion 4A may include apolymer resin having high transparency. Various types of resins can beused as the polymer resin, such as a thermoplastic resin, athermosetting resin, and a resin curable by an energy ray such as anultraviolet ray. Examples of the polymer resin include a cellulose resinsuch as cellulose acetate butyrate and triacetyl cellulose; a polyolefinresin such as polyethylene and polypropylene; a polyester resin such aspolyethylene terephthalate; polystyrene; polyurethane; vinyl chloride;an acrylic resin; a polycarbonate resin; and a silicone resin.

On the other hand, the non-transmissive portion 4B is formed from alight blocking substance capable of absorbing or reflecting light. Assuch a light blocking substance, for example, (1) a dark pigment or adark dye such as in black or gray, (2) a metal such as aluminum andsilver, (3) a dark colored metal oxide, and (4) the above-describedpolymer resins containing a dark pigment or a dark dye can be used.

In the light control layer 4, it is preferable that the width of thetransmissive portion 4A, namely, the width of a polymer resin portionbetween the non-transmissive portion 4B and the non-transmissive portion4B, is greater than the width of the non-transmissive portion 4B toprevent a decrease in light transmissibility of all the light controllayer 4. The width of the transmissive portion 4A may be from 20 to 500μm, and may be from 40 to 200 μm. The width of the non-transmissiveportion 4B may be from 0.5 to 100 μm, and may be from 1 to 50 μm.Furthermore, an angle of the non-transmissive portion 4B may normally bein the range from 0 to 45°. Note that the angle of the non-transmissiveportion 4B refers to an angle with respect to the main surface 4 a ofthe light control layer 4, and the state orthogonal to the main surface4 a (the state illustrated in FIGS. 5A and 5B) is 0 degree.

Such a light control layer 4 can be manufactured, for example, asfollows. First, a layer including a light blocking substance islaminated on one main surface of a polymer film used as the transmissiveportion 4A to form a laminate made from the polymer film/light blockingsubstance. A plurality of such laminates are prepared, and are furtherlaminated to form a light control layer precursor in which the polymerfilm and the light blocking substance are alternately arranged, and arefixed to each other. The precursor is then sliced to have apredetermined thickness in a direction orthogonal to the main surface ofthe precursor, namely, along a laminating direction or a thicknessdirection. As a result, the light control layer 4 is completed.Furthermore, a commercially available product such as “3M (trade name)security/privacy filter” available from 3M Japan Limited can also beused as the light control layer 4.

Note that the configuration (and manufacturing method) of the lightcontrol layer 4 is not limited to the configuration illustrated in FIGS.5A and 5B. For example, the light control layer 4 illustrated in FIG. 6may be employed. The light control layer 4 illustrated in FIG. 6 isconfigured by providing a base member 14 that is light transmissive andthat includes a plurality of grooves 14 a arranged parallel to eachother, and filling the grooves 14 a with a light-absorbing material or alight reflective material. In this case, the non-transmissive portion 4Bextends to a halfway position in the thickness direction of thetransmissive portion 4A.

Next, the reflective layer 5 will be described with reference to FIGS.7A to 7D. Reflection include, diffuse reflection in which incident lightdiffuses at a reflection surface as illustrated in FIG. 7A, specularreflection in which incident light reflects in an opposite direction atthe same angle relative to a reference line perpendicular to thereflective surface as illustrated in FIG. 7B, and retroreflection thatis reflection along a light path of incident light as illustrated inFIG. 7C. In the present embodiment, the reflective layer 5 includes amember that performs retroreflection as illustrated in FIG. 7C. A memberhaving an observation angle of 0.2°, an angle of incidence of 5°, and aretroreflection coefficient of 15 or greater, and preferably 50 orgreater, is employed as the member that performs retroreflection. Notethat a retroreflection coefficient R′ is calculated by “R′=I/Es×A”. Withreference to FIG. 7D, “I” is luminous intensity to the observation angleby a retroreflective surface. “Es” is illuminance received by theretroreflective surface placed perpendicular to a direction of incidentlight. “A” is area where the retroreflective surface receives incidentlight (test piece surface area). Note that “I” is further expressed as“I=Er×d²”. “Er” is illuminance on an optical receiver in thearrangement. “d” is a distance between the test piece surface center anda light receiving reference surface. As a material of such a member thatconstitutes the reflective layer 5, a “3M (trade name) Diamond Grade(trade name) reflection sheet, flexible prism reflection sheet”available from 3M Japan, or the like is employed.

However, the reflective layer 5 may be a member that performs diffusereflection or specular reflection. Furthermore, a light-emitting layerthat emits light by itself may be used instead of the reflective layer5.

In more detail, a configuration as illustrated in FIGS. 8A to 8C may beemployed as a layer configuration of the maker 3. In FIG. 8A, aprotective layer 6 is formed in the main surface 4 a of the lightcontrol layer 4. Furthermore, an adhesive layer 7 is formed in a mainsurface of the reflective layer 5 on the side opposite the light controllayer 4. Furthermore, in FIG. 8B, the light control layer 4 includes aconfiguration in which a threshold value for an angle of incidence oflight to be transmitted can be adjusted by applying a voltage.Furthermore, in FIG. 8C, a print layer 8 in which a two-dimensionalcode, ID, or the like, is described is formed between the light controllayer 4 and the reflective layer 5. The example of FIG. 8C isillustrated in more detail in FIGS. 9A to 9C. When an angle of incidence(namely, a viewing angle) is vertical, contents described in the printlayer 8 can be confirmed in an image, as illustrated in FIG. 9C. Whenthe angle of incidence is too large, the contents described in the printlayer 8 cannot be confirmed in the image, as illustrated in FIG. 9B.

The position detecting unit 22 and the position adjustment unit 23 ofthe flight body 1 perform various operations by using the marker 3configured as described above. The position detecting unit 22 detects aposition of the flight body 1 with respect to the marker 3 based on adifference in luminance of each region E1, E2 of the marker 3 in animage. Furthermore, when the flight body 1 is moved, the positiondetecting unit 22 detects a position of the flight body 1 with respectto the marker 3 based on an aspect of a change in luminance of eachregion E1, E2 of the marker 3 in an image. The position detecting unit22 adjusts a position of the flight body 1 to make a difference inluminance of the region E1, E2 in an image smaller. A state in which adifference in luminance of the region E1, E2 is large means that aposition of the flight body 1 with respect to the marker 3 is greatlyshifted in any of the X-axis direction and the Y-axis direction. Thus,the flight body 1 can be brought closer to the marker 3 by the positionadjustment unit 23 performing adjustment to make a difference inluminance between the region E1, E2 smaller. The position adjustmentunit 23 performs adjustment of a position of the flight body 1 to makeluminance of the marker 3 in an image reach a maximum value. Theluminance of the marker 3 in the image reaches the maximum value when anangle of incidence according to the light source 17 and a viewing angleof the imaging unit 18 are perpendicular to the marker 3. Thus, theposition adjustment unit 23 is capable of positioning the flight body 1directly above the marker 3 by adjusting the position to make theluminance of the marker 3 reach the maximum value. The positionadjustment unit 23 determines whether to land the flight body 1 based onthe luminance of the marker 3.

Next, details of processing by the computation unit 20 will be describedwith reference to FIGS. 10 to 13 and FIGS. 14A to 14D. FIGS. 10 to 13are flowcharts illustrating the details of processing by the computationunit 20. FIGS. 14A to 14D are views illustrating the marker 3 in animage. Note that in the description of the image and the movement of theflight body 1, while the words “vertical” and “horizontal” are used,“vertical” corresponds to the Y-axis direction of the marker 3 describedabove, and “horizontal” corresponds to the X-axis direction of themarker 3.

As illustrated in FIG. 10, the computation unit 20 moves the flight body1 to a target position (step S10). Next, the computation unit 20 turnson the light source 17, and captures an image by the imaging unit 18(step S20). The position detecting unit 22 comprehends the altitude ofthe flight body 1 by determining whether the marker 3 can be recognizedin the image (step S30). Namely, when the marker 3 in the image isdetermined to be too small and not recognizable, the position detectingunit 22 detects that the altitude of the flight body 1 is too high. Whenthe marker 3 in the image is determined to be recognizable, the positiondetecting unit 22 detects that the altitude of the flight body 1 is analtitude that enables processing for landing to be performed. At stepS30, when the marker 3 is determined to be unrecognizable, the positionadjustment unit 23 guides the flight body 1 to slightly lower thealtitude of the flight body 1 (step S40). Subsequently, the processingat step S20 and step S30 is repeated.

At step S30, when the marker 3 is determined to be recognizable, theposition detecting unit 22 detects a position of the flight body 1 withrespect to the marker 3 by determining whether the marker 3 is presentat the center of the image (step S50). Namely, when the marker 3 is atthe center of the image, the position detecting unit 22 can detect thatthe flight body 1 is at a position not shifted from the landing locationunit AP, and when the marker 3 is not at the center of the image, theposition detecting unit 22 can detect that the flight body 1 is at aposition shifted from the landing location unit AP. At step S50, whenthe marker 3 is determined to be not at the center of the image, theposition adjustment unit 23 moves the flight body 1 such that the marker3 is brought to the center of the image (step S60). Subsequently, thecomputation unit 20 turns on the light source 17, and captures an imageby the imaging unit 18 (step S70). Then, the processing at step S50 isrepeated. At step S50, when the marker 3 is determined to be at thecenter of the image, the processing transitions to “A” in FIG. 11.

As illustrated in FIG. 11, the position detecting unit 22 detectsmisalignment in the rotational direction of the flight body 1 withrespect to the landing location unit AP by determining whether therotational direction of the marker 3 is aligned with the rotationaldirection of the image (step S80). As illustrated in FIG. 14A, when themarker 3 is captured obliquely in a longitudinal direction and in alateral direction in the image, the position detecting unit 22 candetect that the flight body 1 is at a position shifted in the rotationaldirection with respect to the landing location unit AP. At S80, when therotational direction of the marker 3 is not aligned with the rotationaldirection of the image, the position adjustment unit 23 rotates afuselage of the flight body 1 (step S90). Subsequently, the computationunit 20 turns on the light source 17, and captures an image by theimaging unit 18 (step S100). Then, the processing at step S80 isrepeated. At step S80, when the rotational direction of the marker 3 isaligned with the rotational direction of the image (for example, thestate illustrated in FIGS. 14B, 14C, 14D), the processing transitions to“B” in FIG. 12.

As illustrated in FIG. 12, the position detecting unit 22 measuresluminance of each quadrant of the marker 3 in the image (step S110). Theposition detecting unit 22 determines whether luminance of the “firstquadrant QD1+third quadrant QD3” including the region E2 and luminanceof the “second quadrant QD2+fourth quadrant QD4” including the region E1are equal (step S120). As a result, the position detecting unit 22 iscapable of detecting whether the flight body 1 is positioned directlyabove the marker 3. Namely, as illustrated in FIG. 14D, when theluminance of the region E1 becomes equal to the luminance of the regionE2 in the image, the luminance of the region E1 and the luminance of theregion E2 are each a maximum value due to the angle of incidence of thelight source 17 and the viewing angle of the imaging unit 18 that becomeperpendicular to the main surface of the marker 3 both in a longitudinaldirection and in a lateral direction. Accordingly, the positiondetecting unit 22 is capable of determining whether the flight body 1 ispositioned directly above the marker 3 by determining the conditionaccording to step S120. Furthermore, the position adjustment unit 23 iscapable of determining whether the flight body 1 is in a state of beingcapable of landing. When the condition is determined to be satisfied atstep S120, the position adjustment unit 23 determines that the flightbody 1 is in a state of being capable of landing, and performs controlsuch that the altitude of the flight body 1 is slowly lowered (stepS130). Subsequently, the flight body 1 makes a landing (step S140), andthe processing by the computation unit 20 ends. On the other hand, whenthe condition is determined not to be satisfied at step S120, theposition adjustment unit 23 determines that the flight body 1 is not ina state of being capable of landing, and transitions to “C” in FIG. 13.

As illustrated in FIG. 13, the position detecting unit 22 determineswhether luminance of the “first quadrant QD1+third quadrant QD3”including the region E2 is greater than luminance of the “secondquadrant QD2+fourth quadrant QD4” including the region E1 (step S160).As a result, the position detecting unit 22 is capable of detectingwhether the flight body 1 is shifted in the vertical direction or thelateral direction with respect to the marker 3.

When the luminance of the second region is high as illustrated in FIG.14B, the condition is determined to be satisfied at step S160. At thistime, the position detecting unit 22 detects that the flight body 1 isat a position shifted in the vertical direction with respect to themarker 3. The position adjustment unit 23 moves the fuselage of theflight body 1 to one side in the vertical direction (step S170). Thecomputation unit 20 turns on the light source 17, and captures an imageby the imaging unit 18 (step S180). The position detecting unit 22determines whether luminance of the “second quadrant QD2+fourth quadrantQD4” has increased (step S190). When the flight body 1 moves in adirection that reduces the shift in the vertical direction, theluminance of the region E1 in the image increases, and when the flightbody 1 moves in a direction that increases the shift in the verticaldirection, the luminance of the region E1 in the image decreases.Accordingly, the position detecting unit 22 is capable of detectingwhether the flight body 1 is at a position that resolves the shift inthe vertical direction by performing the determination of step S190.When the condition is determined to be satisfied at step S190, theprocessing returns to “B” in FIG. 12. On the other hand, when thecondition is determined not to be satisfied at step S190, the positionadjustment unit 23 changes the direction toward the other side in thevertical direction (step S200). Then, the processing is repeated fromstep S170 for the movement in that direction.

When the luminance of the first region is high as illustrated in FIG.14C, the conditions is determined not to be satisfied at step S160. Atthis time, the position detecting unit 22 detects that the flight body 1is at a position shifted in the lateral direction with respect to themarker 3. The position adjustment unit 23 moves the fuselage of theflight body 1 to one side in the lateral direction (step S210). Thecomputation unit 20 turns on the light source 17, and captures an imageby the imaging unit 18 (step S220). The position detecting unit 22determines whether luminance of the “first quadrant QD1+third quadrantQD3” has increased (step S230). When the flight body 1 moves in adirection that reduces the shift in the lateral direction, the luminanceof the region E2 in the image increases, and when the flight body 1moves in a direction that increases the shift in the lateral direction,the luminance of the region E2 in the image decreases. Accordingly, theposition detecting unit 22 is capable of detecting whether the flightbody 1 is at a position that resolves the shift in the lateral directionby performing the determination of step S230. When the condition isdetermined to be satisfied at step S230, the processing returns to “B”in FIG. 12. On the other hand, when the condition is determined not tobe satisfied at step S230, the position adjustment unit 23 changes adirection toward the other side in the lateral direction (step S240).Then, the processing is repeated from step S210 for the movement in thatdirection.

As described above, the processing of FIG. 13 is repeated, and thus theshift in the vertical direction and the lateral direction of flight body1 are gradually eliminated, and eventually the flight body 1 is disposeddirectly above the marker 3, and landing is performed.

Next, actions and effects of the position detection system 100, theposition detection method and the marker 3 according to the presentembodiment will be described.

The position detection system 100 according to the present embodiment isa position detection system 100 for detecting a position of a flightbody 1 moving with respect to a landing location unit AP, the positiondetection system 100 including a light source 17 provided in the flightbody 1, an imaging unit 18 provided in the flight body 1, a marker 3provided in the landing location unit AP, and a position detecting unit22 configured to detect a position of the flight body 1 with respect tothe landing location unit AP based on luminance of an image of themarker 3 acquired by the imaging unit 18, wherein the marker 3 includesa reflective layer 5, a light control layer 4 provided in the reflectivelayer 5 and including a main surface 4 a, and the light control layer 4transmits light having an angle of incidence with respect to the mainsurface 4 a being within a predetermined threshold value.

In the position detection system 100, the flight body 1 is provided withthe light source 17 and the imaging unit 18. Accordingly, the lightsource 17 emits light to the marker 3 of the landing location unit AP,and the imaging unit 18 can acquire an image of the marker 3 in a stateof being irradiated with the light. The marker 3 includes the reflectivelayer 5 and the light control layer 4 provided in the reflective layer5. Furthermore, the light control layer 4 transmits light having anangle of incidence with respect to the main surface 4 a being within apredetermined threshold value. Light having passed through the lightcontrol layer 4 is reflected by the reflective layer 5 and reflected asluminance in the image of the imaging unit 18. That is, when apositional shift between the flight body 1 and the marker 3 is large,since light from the light source 17 does not pass through the lightcontrol layer 4, luminance of the light control layer 4 in the imagereduces. When a positional shift between the flight body 1 and themarker 3 is small, since light from the light source 17 passes throughthe light control layer 4 and is reflected by the reflective layer 5,luminance of the light control layer 4 in the image increases. Theposition detecting unit 22 detects a position of the flight body 1 withrespect to the landing location unit AP based on the luminance of theimage of the marker 3 acquired by the imaging unit 18. Accordingly, theposition detecting unit 22 is capable of easily and accurately detectinga position of the flight body 1 simply by referring to the luminance ofthe light control layer in the image without receiving a special radiowave or the like from the landing location unit AP. As described above,the position detection system 100 is capable of detecting a position offlight body 1 without need of emitting a special radio wave from thelanding location unit AP.

The position detection system 100 further includes a position adjustmentunit 23 configured to adjust a position of the flight body 1 based onluminance of an image of the marker 3 acquired by the imaging unit 18.As described above, when a positional shift between the flight body 1and the marker 3 is small, luminance of the light control layer 4 in theimage increases. Accordingly, since the position adjustment unit 23needs only to adjust a position of the flight body 1 such that theluminance of the light control layer 4 in the image increases,adjustment of the position can be performed easily.

The light control layer 4 includes at least two regions E1, E2, and thethreshold values of the two regions E1, E2 are different from eachother. Appearance of the region E1 in the image and appearance of theregion E2 in the image may differ as a positional relationship betweenthe flight body 1 and the marker 3 changes. In the present embodiment,the position detecting unit 22 is capable of detecting both a positionof the flight body 1 in the X-axis direction and a position of theflight body 1 in the Y-axis direction based on the luminance of theregions E1, E2 in the image. With use of the two regions E1, E2, theposition detecting unit 22 is capable of detecting the position of theflight body 1 in more detail as compared to the case in which only onekind of light control layer 4 is used.

The position detection system 100 further includes a position adjustmentunit 23 configured to adjust a position of the flight body 1 based onluminance of an image of the marker 3 acquired by the imaging unit 18.The position adjustment unit 23 adjusts a position of the flight body 1to make a difference in luminance of the two regions E1, E2 in the imagesmaller. In this case, the position adjustment unit 23 can easilyperform the adjustment of the position by simple processing of reducingthe difference in luminance of the regions E1, E2 in the image, withoutneed of performing complex calculation or the like.

The position detection system 100 further includes a position adjustmentunit 23 configured to adjust a position of the flight body 1 based onluminance of an image of the marker 3 acquired by the imaging unit 18.The position adjustment unit 23 performs adjustment of a position of theflight body 1 to make the luminance of the marker 3 in the image reach amaximum value. In this case, the position adjustment unit 23 can easilyperform the adjustment of the position by simple processing of makingthe luminance of the marker 3 in the image reach a maximum value withoutneed of performing complex calculation and the like.

An angle equal to or less than the threshold includes an angle that isperpendicular to the main surface 4 a. In this case, when the mainsurface 4 a is perpendicularly irradiated with light from the lightsource 17, luminance of the light control layer 4 in the image alsoincreases.

The movable body is the flight body 1, and the light source 17 emitslight in a direction perpendicular to a horizontal plane FP of theflight body 1. In this case, the position adjustment unit 23 easilyperforms the adjustment of the position such that the horizontal surfaceFP of the flight body 1 and the main surface of the marker 3 areparallel.

The position detection system 100 further includes a position adjustmentunit 23 configured to adjust a position of the flight body 1 based onluminance of an image of the marker 3 acquired by the imaging unit 18.The position adjustment unit 23 determines whether to land the flightbody 1 in flight based on the luminance of the marker 3. In this case,the position adjustment unit 23 is capable of easily determining whetherlanding is possible based on the luminance of the marker 3 in the imagewithout need of performing complex calculation or the like.

The position detection method according to the present embodiment is aposition detection method for adjusting a position of a flight body 1moving with respect to a landing location unit AP, the method includingthe steps of: emitting light from a light source 17 provided in theflight body 1 to a marker 3 provided in the landing location unit AP;acquiring an image including the marker 3; and detecting a position ofthe flight body 1 with respect to the landing location unit AP based onluminance of an image of the marker 3 acquired; wherein the marker 3includes a reflective layer 5, and a light control layer 4 provided inthe reflective layer 5 and including a main surface 4 a, and the lightcontrol layer 4 transmits light having an angle of incidence withrespect to the main surface 4 a being within a predetermined thresholdvalue.

According to this position detection method, the same actions andeffects as the position adjustment unit 23 of the position detectionsystem 100 described above can be obtained.

The marker 3 is a marker 3 including a reflective layer 5, and a lightcontrol layer 4 provided in the reflective layer 5, wherein the lightcontrol layer 4 transmits light having an angle of incidence withrespect to the main surface 4 a being within a predetermined thresholdvalue, the light control layer 4 includes at least two regions E1, E2,and the threshold values of the two regions are different from eachother, and the reflective layer 5 reflects light having passed throughthe light control layer 4, and luminance of the reflected light is usedto detect a position of the marker 3.

According to this marker 3, the same actions and effects as the positiondetection system 100 described above can be obtained by providing themarker 3 in the landing location unit AP and performing detection of aposition and adjustment of a position of the flight body 1.

The present disclosure is not intended to be limited to the embodimentsdescribed above.

A structure of the marker 3 is not limited to the embodiments describedabove. For example, a marker according to each of forms as illustratedin FIGS. 15A to 15F may be employed. As illustrated in FIG. 15A, areflective region 51 having a high reflectance may be formed in a centerportion. In this case, when another flight body 1 has already completedthe landing, the reflective region 51 becomes in a state of not showingin an image. Accordingly, the flight body 1 preparing for the landing iscapable of comprehending that the marker 3 is occupied by another flightbody 1.

As illustrated in FIGS. 15B to 15E, the marker 3 may include a structurein which a positional relationship of each quadrant can be comprehendedin an image. For example, the marker 3 in FIG. 15B includes an alignmentmark 52 at a corner portion. The alignment mark 52 is provided bypartially forming a low luminance region in a high luminance region. Thealignment mark 52 is not provided at a corner portion on the fourthquadrant QD4 side, but is provided at three other corner portions. Themarker 3 in FIG. 15C includes a low luminance region 53 at four edgeportions, and includes a high luminance region 54 only in the edgeportion of the low luminance region 53 above the first quadrant QD1 andthe second quadrant QD2. The marker 3 in FIG. 15D includes aconfiguration in which the region E1 and the region E2 are alternatelydisposed in a two row×three column pattern, and only a quadrant in thesecond row and the second column is shifted downward. The marker 3 inFIG. 15E includes a structure in which the third quadrant QD3 and thefourth quadrant QD4 each have a rectangular shape extending downward.When, as with the marker 3 of each of FIGS. 15B to 15E, a positionalrelationship between the quadrants can be comprehended in an image, theposition detecting unit 22 easily detects a position of the flight body1 with respect to each quadrant of the marker 3, and the positionadjustment unit 23 easily performs the adjustment of the position.

As with the marker 3 illustrated in FIG. 15F, regions E3, E4 with alouver film including an array extending in an oblique direction may beprovided, in addition to the region E1 with a louver film including anarray extending straight in the lateral direction and the region E2 witha louver film having an array extending straight in the verticaldirection.

Furthermore, a light control layer 4 illustrated in FIG. 16 may beemployed. This light control layer 4 includes three regions E1 a, E1 b,E1 c having different pitches while the directions of the arrays oflouver films are the same. A threshold value of an angle of incidencefor transmitting light increases in the order of the regions E1 a, E1 b,E1 c. In this case, as illustrated in images GF1 to 4, a difference inluminance of the regions in the images increases as an angle ofincidence of the light source 17 (viewing angle of the imaging unit 18)increases. Accordingly, the position detecting unit 22 easilycomprehends the degree of shift of the flight body 1 with respect to themarker 3.

Furthermore, a light control layer 60 illustrated in FIGS. 17A to 17Cmay be employed. As illustrated in FIG. 17A, the light control layer 60includes a grid-like louver film. As such a light control layer 60, forexample, a member described in JP 2017-522598 T is used. In the lightcontrol layer 60 illustrated in FIG. 17B, reflection luminance formsconcentric circular intensity distribution, and the closer to thecenter, the higher the luminance. For example, the position adjustmentunit 23 linearly moves the flight body 1 along a movement position ML1.At this time, since reflection luminance is as illustrated in a graphBL1 in FIG. 17C, the position adjustment unit 23 identifies a positionat which the reflection luminance is maximum. The position adjustmentunit 23 linearly moves the flight body 1 along a movement position ML2in the vertical direction from such a position, and identifies aposition at which the reflection luminance is maximum. Accordingly, theflight body 1 is disposed directly above a center position of themarker. Note that when a movement position ML1′ is greatly shifted fromthe center, the reflection luminance changes smoothly as in a graph BLof FIG. 17C. In this case, the position adjustment unit 23 regards acenter point of rising positions of edge portions of both ends of thegraph BL as a position at which the luminance reflection is maximum.

Furthermore, the position detection system of the present embodiment maybe used for measurement of a vibration frequency and inclination. Asillustrated in FIG. 18A, when an object provided with the marker 3 tiltswith respect to the light source 17 and the imaging unit 18 set at anangle of incidence θ (see FIGS. 18B and 18C), a louver angle of thelight control layer 4 also changes. As a result, reflection intensitychanges in accordance with the louver angle (see FIG. 18D). Accordingly,the position detection system continuously measures reflectionintensity, and thus a relative angle of the object with respect to theimaging unit 18 can be detected, and vibration measurement can beperformed. Namely, the position detection system is capable of detectingvibration of the object based on a time-series change of an angle. Notethat in the figures, a retroreflective sheet is omitted.

To perform the measurement, change in reflection intensity with respectto an angle needs to be linear, and thus observation needs to beperformed at a desired angle of incidence. For example, there is aproblem of not being able to comprehend a direction of inclination whenan angle of incidence is 0°. As the countermeasure, as illustrated inFIG. 19A, a guide sheet 65 including a louver having an inclination of areference angle θ is disposed at a position adjacent to a detectionsheet 66. To separate reflected light for the detection sheet 66 as themarker 3 and reflected light for the guide sheet 65 configured to set anangle of incidence, a light source 17A of visible light and a lightsource 17B of IR light are prepared as two types of light sources havingdifferent wavelengths. Furthermore, an imaging unit 18A of visible lightand an imaging unit 18B of IR light are prepared. A filter (lightabsorbing layer) configured to select light is applied to a surface ofeach sheet. In the example illustrated in FIGS. 19A and 19B, a filter 67configured to absorb visible light is provided in the detection sheet 66and irradiation with visible light is performed. Then, an angle ofincidence at which reflection intensity is strongest is determined fromthe guide sheet 65, and the imaging unit 18 and the light source 17 arefixed. A filter 68 configured to absorb IR light is provided in theguide sheet 65, irradiation with IR light from the light source 17B isperformed in that state, and inclination or a vibration frequency of atarget TG is measured (see FIG. 19B).

The details of processing of the measurement of a vibration frequencyand inclination by the position detection system will be described withreference to FIG. 20. First, the target TG is moved to an observationposition (step S300). Next, preparation to set an angle of incidence isperformed as illustrated in FIG. 19A (step S310). Next, determination isperformed as to whether maximum intensity has been identified (stepS320). When the maximum intensity cannot be identified, the angle ofincidence is changed (step S330) and the processing is repeated fromstep S310. When the maximum intensity is identified, an observationdistance for each device is fixed (step S340). Next, the detection sheet66 is irradiated with IR light from the light source 17B, and an imageof the detection sheet 66 is captured by the imaging unit 18 (stepS350). Then, measurement of a vibration frequency and inclination of thetarget TG is performed by performing reflected light intensitymeasurement (step S360).

This angle detection method is an angle detection method for detecting arelative angle (of a light source and an imaging unit) with respect to atarget TG, the method including the steps of emitting light from a lightsource 17B to a marker 3 provided in the target TG, acquiring an imageincluding the marker 3; and detecting a relative angle with respect tothe target TG based on luminance of the image of the marker 3 acquired,wherein the marker 3 includes a reflective layer 5, and a light controllayer 4 provided in the reflective layer 5, and the light control layer4 transmits light having a predetermined angle of incidence with respectto a main surface 4 a.

According to this angle detection method, the measurement of a vibrationfrequency and inclination can be performed by simple work of capturingand observing the marker 3 by providing the marker 3 in the target TGwithout using a device such as a device that emits a specialelectromagnetic wave.

Furthermore, as illustrated in FIGS. 21A and 21B, the measurement of avibration frequency and inclination as described above may be performedin two axes. The marker 3 here includes four quadrants QD1 to QD4. Inthe second quadrant OD2 and the fourth quadrant QD4, a louver having anangle θ similar to the guide sheet 65 of FIGS. 19A and 19B is disposedin a vertical direction, and a blue bandpass filter 71 is provided in afront face. In the first quadrant OD1 and the third quadrant QD3, a 90°louver is disposed in a horizontal direction, and a red bandpass filter72 is provided in the front face. As with the single axis measurementillustrated in FIGS. 19A and 19B, the guide sheet 65 is used todetermine a desired angle of incidence with respect to the verticaldirection. At this time, a filter 73 configured to transmit IR lightonly and absorb visible light is provided in a front face of the guidesheet 65. In this way, the light source 17 of visible light formeasurement, a detector 18C provided with a red bandpass filter, and adetector 18D provided with a blue bandpass filter are fixed at an angleθ. As a result, the position detection system is capable ofsimultaneously measuring a tilt angle in the vertical direction and atilt angle in the lateral direction by measuring output by the detectors18C, 18D.

Furthermore, the position detection system of the present embodiment canalso be used when the flight body 1 irradiates a target object withlaser light. For example, it has been proposed to mount a sensor formonitoring deterioration progress of a social infrastructure such as abridge and for detecting damage due to an earthquake and the like, buthow to supply the sensor with a power source for a long time has been aproblem.

For this problem, a solar cell 80 is disposed at the center of themarker 3 according to the embodiments described above, as illustrated inFIG. 22B. Then, as illustrated in FIG. 22A, the marker 3 is provided ata predetermined position of a structure ST (stationary body) that is astationary body. Then, a normal direction of the solar cell 80 and theflight body 1 is identified by the same method as the method for landingthe flight body 1 described in the embodiment of FIG. 1. Next, theflight body 1 irradiates with laser light from a laser device 81 at awavelength at which conversion efficiency of the solar cell 80increases, to generate and feed power to the sensor connected to thesolar cell 80.

In the embodiments described above, the marker is provided in thelanding location unit and the light source and the imaging unit areprovided in the moving body, but the marker may be provided in themoving body and the light source and the imaging unit may be provided inthe landing location unit.

REFERENCE SIGNS LIST

1 . . . Flight body (moving body), 3 . . . Marker, 4, 60 . . . Lightcontrol layer, 5 . . . Reflective layer, 17 . . . Light source, 18 . . .Imaging unit, 22 . . . Position detecting unit, 23 . . . Positionadjustment unit, AP . . . Landing location unit (stationary body), TG .. . Target (stationary body), ST . . . Structure (stationary body), andFP . . . Horizontal plane.

1. A position detection system for detecting a position of a movablebody moving with respect to a stationary body, the position detectionsystem comprising: a light source provided in one of the stationary bodyand the movable body; an imaging unit provided in one of the stationarybody and the movable body; a marker provided in the other of thestationary body and the movable body; and a position detecting unitconfigured to detect a position of the movable body with respect to thestationary body based on luminance of an image of the marker acquired bythe imaging unit; wherein the marker includes a reflective layer, and alight control layer provided in the reflective layer and including amain surface, and the light control layer transmits light having anangle of incidence with respect to the main surface being within apredetermined threshold value.
 2. The position detection systemaccording to claim 1, further comprising a position adjustment unitconfigured to adjust a position of the movable body based on luminanceof an image of the marker acquired by the imaging unit.
 3. The positiondetection system according to claim 1, wherein the light control layerincludes at least two regions and the threshold values of the tworegions are different from each other.
 4. The position detection systemaccording to claim 3, further comprising a position adjustment unitconfigured to adjust a position of the movable body based on luminanceof an image of the marker acquired by the imaging unit, wherein theposition adjustment unit adjusts a position of the movable body to makea difference in luminance between the two regions in the image smaller.5. The position detection system according to claim 1, furthercomprising a position adjustment unit configured to adjust a position ofthe movable body based on luminance of an image of the marker acquiredby the imaging unit, wherein the position adjustment unit adjusts aposition of the movable body to make luminance of the marker in theimage reach a maximum value.
 6. The position detection system accordingto claim 1, wherein an angle having the threshold value or less includesan angle perpendicular to the main surface.
 7. The position detectionsystem according to claim 1, wherein the movable body is a flight body,and the light source emits light in a direction perpendicular to ahorizontal plane of the flight body.
 8. The position detection systemaccording to claim 1, further comprising a position adjustment unitconfigured to adjust a position of the movable body based on luminanceof an image of the marker acquired by the imaging unit, wherein theposition adjustment unit determines whether to land the movable body inflight based on luminance of the marker.
 9. A position detection methodfor adjusting a position of a movable body moving with respect to astationary body, the method comprising the steps of: emitting light froma light source provided in one of the stationary body and the movablebody to a marker provided in the other of the stationary body and themovable body; acquiring an image including the marker; and detecting aposition of the movable body with respect to the stationary body basedon luminance of an image of the marker acquired; wherein the markerincludes a reflective layer, and a light control layer provided in thereflective layer and including a main surface, and the light controllayer transmits light having an angle of incidence with respect to themain surface being within a predetermined threshold value.
 10. An angledetection method for detecting a relative angle with respect to atarget, the method comprising the steps of: emitting light from a lightsource to a marker provided in the target; acquiring an image includingthe marker; and detecting the relative angle with respect to the targetbased on luminance of an image of the marker acquired; wherein themarker includes a reflective layer, and a light control layer providedin the reflective layer and including a main surface, and the lightcontrol layer transmits light having a predetermined angle of incidencewith respect to the main surface.
 11. The angle detection methodaccording to claim 10, wherein vibration of the target is detected basedon a time-series change of an angle.
 12. A marker comprising: areflective layer; and a light control layer provided in the reflectivelayer and including a main surface, wherein the light control layertransmits light having an angle of incidence with respect to the mainsurface being within a predetermined threshold value, the light controllayer includes at least two regions, and the threshold values of the tworegions are different from each other, and the reflective layer reflectslight having passed through the light control layer, and luminance ofthe reflected light is used to detect a position of the marker.